In the prior art, numerous apparatus have been proposed to fold flexible material in configurations such as tubes or the like. In these types of apparatus, a thin film such as a plastic sheet or web is continuously run in one direction through a folding apparatus to fold the plastic sheet or film in a particular configuration.
The following United States Patents disclose prior art apparatus used for folding thin flexible material:
U.S. Pat. No. 228,162 to Appel discloses a tube-machine for making pleated tubes for paper bags. The machine of Appel incorporates formers in combination with guides to form the pleated tubes. The design of Appel lacks any defined geometry with respect to the formers or guides.
U.S. Pat. No. 1,501,499 to Swift, Jr. discloses a web folding machine utilizing a plurality of folding bars to produce the desired configuration of the folded web. The initial folding bars do not support the flexible material when the design is set to fold wider material. In addition, the folding bars must be individually adjusted to change the fold spacing.
U.S. Pat. No. 1,613,505 to Deligianes et al. discloses a paper folding device including three triangularly shaped single folders that require four turning edges to make a single fold. In order to make two folds, the single folding operation would be repeated requiring a total of eight turning edges.
U.S. Pat. No. 2,190,823 to Cloud discloses a method and apparatus for folding strips of paper or the like. The apparatus includes a plurality of adjustable plates or strips that are removable for cleaning.
U.S. Pat. No. 2,490,930 to Thompson discloses an apparatus for forming tubes from sheet material. The material is guided over rods that are individually adjusted. The geometry of the rods produces a flattened tube with a seam aligned in the center of the tube. The apparatus of Thompson does not include features to adjust the width of the apparatus as well as means to position the seam off-center of the flattened tube axis.
U.S. Pat. No. 2,540,844 to Strauss discloses a web folding machine which includes adjustable width folding means. However, the amount of material folded per side is limited to less than half of the distance between folds. This machine is designed for folding over the edges of material rather than producing flattened tubes.
U.S. Pat. No. 4,304,561 to Shingo discloses a film folding device which produces a single fold. In order to produce a double fold, an additional set of tooling is required.
In view of the prior art discussed above, a need has developed to provide an improved plastic film folding tool which is adaptable to produce single or double folds. In addition, a need has developed to provide folding tooling which minimizes contact area between the plastic film and tooling components to reduce damage to the film as well as increase yield.
In response to this need, the present invention provides an improved adjustable plastic film folding tool assembly which includes features to fold plastic film in varied widths as well as having the ability to shift the film overlap from the center towards one edge. None of the prior art cited above teaches or fairly suggests an adjustable plastic film tooling assembly including all of the features of the present invention.